DE102014112876B4 - Surface-modifiable injection-moulded body and process for its production - Google Patents

Abstract

Surface-modified injection molding (1), produced from a thermoplastic polymer matrix (2) and a second polymeric material (3), the thermoplastic polymer matrix (2) being selected from the group consisting of acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile ( SAN), polystyrene (PS), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyamide (PA), or mixtures thereof, and the second polymeric material (3) is a functionalized thermoplastic polyolefin elastomer (POE), is an olefinic block copolymer (OBC) or a mixture thereof, which is at least partially present as a surface layer and is suitable as a hot-melt adhesive for connecting the injection-molded body (1) to another component, the polymer matrix (2) and the second polymeric material (3 ) have different weight-average molecular weights and polarities, the second polymeric material (3) being contained in a proportion of 10-30% by mass, u nd wherein the second polymeric material (3) has an average molecular weight of 11,000 to 37,000 g/mol.

Description

technical field

The present invention relates to a surface-modifiable injection molding comprising a thermoplastic polymer matrix and a second polymeric material at least in regions, as well as a corresponding method for its production and use.

In the meantime, plastics account for between 15 and 20 percent by weight in automobile construction, and the trend is rising. These are often exterior and interior parts that receive their corresponding optical, haptic and functional properties by gluing injection molded components with different surface decors. The increasing demands on quality and cost-effectiveness as well as resource efficiency, but also global competitive pressure, require ever more economical, sustainable and flexible bonding processes.

In particular, plastic parts as injection moldings for automotive interiors, such as instrument panels, door panels or center consoles, are provided with surface decorations such as leather or foil for improved appearance, which are fixed and joined to the moldings using dispersion adhesive or hotmelt adhesive.

A step for pre-treating the surface of the molded part is usually required here in order to ensure suitable surface tension while maintaining defined process windows. The adhesion properties can usually be optimized by activating the surface by flaming, plasma treatment or gas-phase fluorination.

However, a disadvantage of these methods is that they require at least one additional step in the production process. In addition, additional, sometimes complex and expensive additional equipment is required. Above all, the treatment of the surfaces with acids and solvents also represents a high level of environmental pollution.

State of the art

Currently, the trend towards fewer bonding steps, for example through the integration of a bonding function in the injection molding process, is also very popular for add-on parts made of plastic.

Polypropylene and reinforced polypropylene are inexpensive and commonly used plastics for injection molded parts. Due to the non-polar properties of polypropylene, further processing or finishing of the injection molded parts is in most cases not possible without pre-treatment. Pre-treatment is necessary, especially when gluing and painting, otherwise the adhesives and paints will not adhere sufficiently to the surface.

With so-called "bonding on demand", the adhesive or an adhesive layer is applied to the injection-molded part in a process step immediately after the injection molding.

1. (a) Auftragen einer Schicht eines festen Klebemittels des Typs Hot Melt 100%, basierend auf reaktionsfähigem Polyurethan, und zwar mit Hilfe einer Rakel oder einer Rolle, auf einer der beiden Oberflächen eines Laminats, einer Folie oder eines Films zur Beschichtung, insbesondere aus Polymer-Material oder aus natürlichem beziehungsweise technischem Stoff;
2. (b) Auflegen des zur Beschichtung gedachten Laminats, der Folie oder des Films auf die entsprechende Oberfläche der zu veredelnden Platte;
3. (c) Vorwärmen des zur Beschichtung gedachten Laminats, beziehungsweise der Folie oder des Films;
4. (d) Kaschieren des zur Beschichtung gedachten Laminats, der Folie oder des Films auf die zu veredelnde Platte durch Warmpressen.

For example disclosed DE 103 49 177 A1 a process for refining previously formed panels with the steps:

1. (a) Application of a layer of solid adhesive of the 100% Hot Melt type, based on reactive polyurethane, using a squeegee or roller, to one of the two surfaces of a laminate, sheet or film for coating, in particular made of polymer -material or made of natural or technical substance;
2. (b) placing the laminate, foil or film to be coated on the appropriate surface of the panel to be finished;
3. (c) preheating of the laminate, foil or film to be coated;
4. (d) Lamination of the laminate, foil or film intended to be coated onto the panel to be finished by hot pressing.

Comparable methods can be found in particular in the field of metal-plastic composites.

EP 2 374 593 A1 discloses an injection molding process for modifying a surface of a molded body made of apolar polymer, a multilayer film suitable for this purpose, and a polymer molded part with a modified surface. In the method, a multi-layer film with at least a first apolar layer and a second layer with at least one surface property that differs from the first layer is back-injected. Back injection molding of films is a well-known technology in which a film is first placed in the cavity of an injection mold or clamped onto the injection mold. The foil is pressed into the cavity and is deformed according to the shape of the cavity. A polymer is then injected into the cavity, with the side of the film facing the polymer bonding to the polymer. As a result, molded parts can be obtained which are covered with a film. Today, mainly decorative foils are back-injected, such as with the "In-Mold-Decoration" (IMD) technique.

After EP 2 374 593 A1 However, a multilayer film with at least one apolar layer and at least one second layer with at least one surface property different from the first layer is inserted into the cavity of an injection molding tool in such a way that the first apolar layer faces the interior of the cavity while the second layer is on the inner wall of the cavity comes to rest. The apolar polymer is then injected into the interior of the mold. The injected polymer and the first apolar layer of the multilayer film are in contact in the mold and subsequently bond.

The second layer of the multilayer film has at least one surface property that differs from the first apolar layer.

US 2004/0228971 A1 relates to painted polyacetal moldings comprising: a polyoxymethylene (POM) molding as a polyacetal substrate comprising 90-99.5% by weight polyacetal and 0.5-10% by weight of a semi-crystalline or amorphous non-polyacetal thermoplastic resin having a molecular weight of 1,000 up to 50,000, usually 5,000-50,000; and a paint on the polyacetal substrate from a solventborne, waterborne or powder 1K paint system. In this regard, the surface of the polyacetal substrate is pretreated to facilitate exposure and accessibility of the semicrystalline or amorphous non-polyacetal thermoplastic resin in the substrate for the applied paint. The paint applied is a thermoplastic or partially thermoplastic paint. This provides a painted polyacetal molding with improved paint adhesion and consistent physical-mechanical properties.

the EP 2 151 830 A1 discloses a polymer molding with conductive structures on the surface, and a method for its production.

Description of the invention

The object of the present invention is therefore to provide an injection molding or plastic molding whose adhesion and wetting properties can be intrinsically modified in a simple manner in such a way that the number of process steps for gluing the molding and the costs for the tools are reduced and at the same time the quality requirements are met the bonding are fulfilled.

A further object of the invention is to provide a corresponding method in which the adhesion and wetting properties of a molded part surface are functionally improved during or after the injection molding without additional effort.

According to the invention, this object is achieved by an injection molded body having the features of claim 1 and a method of claim 8 .

The basic idea of the present invention is that the surface-modifiable injection molded body comprises a thermoplastic polymer matrix and at least in some areas a second polymeric material, the polymer matrix and the second polymeric material having different weight-average molecular weights and polarities and the second polymeric material being suitable as a hot-melt adhesive.

In other words, the second polymeric material is already integrated as an adhesive component in the injection molded body with a thermoplastic polymer matrix. In the finished, cooled state, the adhesive component is present at least in regions as a separate layer, for example as a surface layer. For further processing or gluing, the desired molding area is heated. the A surface activated in this way behaves as if an adhesive had been applied. This is noticeable on the one hand in the stickiness of the surface and in an increase in surface tension, since the polar component migrates to the surface.

In view of the prior art, it was surprising and unforeseeable for the person skilled in the art that the object on which the present invention was based could be achieved with the aid of the injection molded body according to the invention and the method for its production. A particular advantage of the invention is that with the injection molded body and in the proposed method, the step of separate activation of the substrate and an external application of adhesive are dispensed with entirely.

This not only eliminates investment costs for the adhesive application and/or activation units, but also the operating costs associated with the activation units and the adhesive application.

According to an advantageous further development of the surface-modifiable injection molded body, it is provided that the thermoplastic polymer matrix and the second polymeric material at least partially form a phase separation under the action of heat, with enrichment of the second polymeric material on the surface of the injection molded body. This means that before and during the injection molding, the thermoplastic polymer matrix and the tackifying second polymer component are initially present in the injection molding as a largely homogeneous mixture. The surface-modifiable injection molding is modified under the influence of heat, for example by heat or radiation, and subsequent cooling. Due to the low average molecular masses and densities of the second polymer component, but also due to its increased polarity compared to the matrix material, it moves relatively freely within the polymer matrix when heated. During cooling, a thermodynamically controlled phase separation takes place, which can be used as an adhesive function.

According to the invention, the thermoplastic polymer matrix is selected from the group consisting of acrylonitrile butadiene styrene (ABS), styrene acrylonitrile (SAN), polystyrene (PS), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyamide (PA). ) or mixtures thereof. These can also be fiber-reinforced.

According to the invention, the second polymeric material is a functionalized thermoplastic polyolefin elastomer (POE), an olefinic block copolymer (OBC), or a blend thereof.

In this case, the second polymeric material can preferably be melted and resolidified.

According to the invention, the second polymeric material is contained in the surface-modifiable injection-molded article in a proportion of 5-10-30% by mass, preferably 10-25% by mass.

According to the invention, the second polymeric material has an average molecular weight of 11,000 to 37,000 g/mol.

The surface-modifiable injection molding or the first and/or second polymer preferably has additives that can be coupled to microwaves.

The additives that can be coupled by microwaves preferably contain carbon fibers, carbon nanotubes, graphene or the like. The shaped body can thus optionally be heated exclusively by microwave treatment.

1. a) Bereitstellung einer thermoplastische Polymermatrix mit einem zweiten polymeren Material, wobei die Polymermatrix und das zweite polymere Material unterschiedliche gewichtsmittlere Molekulargewichte und Polaritäten aufweisen und das zweite polymere Material als Klebstoff geeignet ist, wobei das zweite polymere Material in einem Mengenanteil von 10-30 Ma-% enthalten ist, und wobei das zweite polymere Material ein mittleres Molekulargewicht von 11 000 bis 37 000 g/mol aufweist;
2. b) Aufschmelzen, Spritzgießen und Abkühlen des Materials in einem Spritzgießwerkzeug, wobei die thermoplastische Polymermatrix ausgewählt ist aus der Gruppe bestehend aus Acrylnitril-Butadien-Styrol (ABS), Styrol-Acrylnitril (SAN), Polystyrol (PS), Polycarbonat (PC), Polyethylen(PE), Polypropylen (PP), Polyamide (PA), oder Mischungen daraus, und die thermoplastische Polymermatrix und das zweite polymere Material beim Aufschmelzen zumindest teilweise eine Phasentrennung unter Anreicherung des zweiten polymeren Materials an der Oberfläche des Spritzgussformkörpers ausbilden;
3. c) Entfernen des Formkörpers aus dem Spritzgießwerkzeug;
4. d) Erwärmen des Spritzgussformkörpers, wobei das zweite polymere Material zur Verbindung des Spritzgussformkörpers mit einem weiteren Bauteil als Klebstoff wirkt.

The method according to the invention for producing a surface-modified shaped body comprises the following steps:

1. a) Provision of a thermoplastic polymer matrix with a second polymeric material, wherein the polymer matrix and the second polymeric material have different weight-average molecular weights and polarities and the second polymeric material is suitable as an adhesive, the second polymeric material in a proportion of 10-30 Ma- % is included, and wherein the second polymeric material has an average molecular weight of 11,000 to 37,000 g/mol;
2. b) melting, injection molding and cooling of the material in an injection mold, the thermoplastic polymer matrix being selected from the group consisting of acrylonitrile butadiene styrene (ABS), styrene acrylonitrile (SAN), polystyrene (PS), polycarbonate (PC), Polyethylene (PE), Polypropylene (PP), Polyamide (PA), or blends thereof, and the thermoplastic polymer matrix and the second polymeric material at least partially form a phase separation during melting with enrichment of the second polymeric material on the surface of the injection molded body;
3. c) removing the molding from the injection mold;
4. d) heating of the injection molded body, wherein the second polymeric material acts as an adhesive for connecting the injection molded body to a further component.

The injection molded body is preferably heated in a gradient-controlled manner, so that a selective, controlled enrichment of the second polymeric material takes place on a predeterminable surface or surface area of the injection molded body. It is therefore conceivable that only a selected surface area of the shaped body is heated and bonded to another component.

The injection molded body is preferably heated gradient-controlled in such a way that the second polymeric material is selectively enriched on a visible surface of the injection molded body and this is then connected or glued to, for example, a flat decorative part. By heating and subsequent gluing of the heated, surface-modifiable injection molded body to a suitable decorative part, a molded body is thus advantageously provided in which the method step of applying the adhesive can be dispensed with. The adhesive is already intrinsically contained in the molded body and can be selectively released by simply heating it.

examples

The invention is explained in more detail below by means of a number of examples, without thereby wishing to restrict the invention.

The examples tabularly show various functionalized polyolefin elastomers (POE), olefinic block copolymers (OBC) or mixtures thereof as the second polymeric material according to the invention.

The so-called "Infuse™" (Dow Chemical Company) olefin block copolymers (OBC) and the "Affinity™" GA (Dow Chemical Company) polyolefin elastomers (POE, TPO), which have recently become commercially available, form an example of the starting point for hot-melt adhesive technology for use in injection molded part.

In principle, both polymers have extremely low mean molecular masses and densities compared to conventional polyolefins, but they also have a high polarity. The other special physicochemical properties have been discussed elsewhere.

"Infuse™" (Dow Chemical Company) olefin block copolymers (OBC) are ethylene and α-olefin copolymers composed of alternating semi-crystalline and elastomeric blocks or segments that are randomly distributed in a multi-block architecture and are critical to their hot melt -Contribute adhesive functionality.

The following tables show various properties of the "Affinity™" GA (Dow Chemical Company) polyolefin elastomers (POE, TPO).

1. a) Polymermatrix aus Polypropylen (PP)
2. b) „Infuse 9817“: Copolymer aus Ethylen mit Octen, Schmelzpunkt 120 °C, Biegemodul 23 MPa, Dichte 0,877 g/m3, Schmelzindex 15 g/10 min vor der Pfropfung und nach der Pfropfung 4 g/10 min
3. c) „Affinity™ GA“ Polyolefin Elastomer

Raw materials of the examples:

1. a) Polymer matrix made of polypropylene (PP)
2. b) "Infuse 9817": copolymer of ethylene with octene, melting point 120 °C, flexural modulus 23 MPa, density 0.877 g/m3, melt index 15 g/10 min before grafting and 4 g/10 min after grafting
3. c) “Affinity™ GA” polyolefin elastomer

Example 1:

Infuse 9817 is mixed with PP in the melt on an injection molding machine in a proportion of 10-30% by mass and applied as a flat molding.

1. a) Zwei miteinander verklebte Formkörper weisen eine Zugfestigkeit gemäß DIN > 7000 N auf.
2. b) Ein mit einem flächigen Dekor (PVC, PUR, geschäumt) verklebter Formkörper weist nach Erwärmung auf ca. 180°C eine Zugfestigkeit gemäß DIN > 10-50 N auf.

This is followed by heating, gluing and an adhesive strength test and the molded body:

1. a) Two moldings bonded together have a tensile strength according to DIN > 7000 N.
2. b) A shaped body bonded with a flat decoration (PVC, PUR, foamed) has a tensile strength according to DIN > 10-50 N after heating to approx. 180°C.

The tensile strength measured corresponds in the order of magnitude to a tensile strength achieved by conventional adhesive application.

Example 2:

1. a) Eine Formkörperoberfläche aus reinem PP weist als Referenzmaterial nach Erwärmung eine Oberflächenspannung von 28 mN/m gemäß DIN auf.
2. b) Eine Formkörperoberfläche aus erfindungsgemäßen PP + TPO/OBC weist nach Erwärmung eine Oberflächenspannung von 32-34 mN/m gemäß DIN auf.

Furthermore, analysis methods for measuring the surface tension are used to characterize the surface and the distribution of the adhesive:

1. a) A molding surface made of pure PP as a reference material has a surface tension of 28 mN/m according to DIN after heating.
2. b) A molding surface made of PP+TPO/OBC according to the invention has a surface tension of 32-34 mN/m according to DIN after heating.

The significant increase in surface tension, which is accompanied by a noticeable stickiness of the surface, proves the accumulation of the polar TPO/OBC polymer component on the surface.

character list

Individual embodiments of the injection molded body and its production and use are described in more detail below with reference to the drawings.

• 1 eine schematische Darstellung eines erfindungsgemäßen oberflächenmodifizierbaren Spritzgussformkörpers mit einer thermoplastische Polymermatrix und zumindest bereichsweise einem zweiten polymeren Material;
• 2 eine schematische Darstellung der strukturellen Veränderung bzw. Phasentrennung eines oberflächenmodifizierbaren Spritzgussformkörpers unter Wärmeeinfluss; und
• 3 eine schematische Darstellung des Verklebens eines erwärmten oberflächenmodifizierten Spritzgussformkörpers mit einem Dekorteil.

Show in it:

• 1 a schematic representation of a surface-modifiable injection molding according to the invention with a thermoplastic polymer matrix and at least in some areas a second polymeric material;
• 2 a schematic representation of the structural change or phase separation of a surface-modifiable injection molded body under the influence of heat; and
• 3 a schematic representation of the gluing of a heated surface-modified injection molded body with a decorative part.

The general structure of the injection molded body during injection molding results from a thermoplastic polymer matrix, represented as large balls. The matrix can be made of acrylonitrile butadiene styrene (ABS), styrene acrylonitrile (SAN), polystyrene (PS), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyamide (PA), in each case fiber-reinforced or unreinforced or their mixtures exist.

Incorporated into this matrix are "InfuseTM" (Dow Chemical Company) olefin block copolymers (OBC) and/or "AffinityTM" GA (Dow Chemical Company) polyolefin elastomers (POE), which form the tackifying component of the molded body and act as small balls are shown. These differ from the matrix material in particular by a lower average molecular weight and a comparatively high polarity.

Before and during injection molding, the thermoplastic polymer matrix and the tackifying olefin block copolymers (OBC) and/or polyolefin elastomers (POE) are initially present as a largely homogeneous mixture in the injection molding granules and then as a homogeneous, statistical mixture in the injection molding process.

2 illustrates the structural change of the surface-modifiable injection molded body under the influence of heat, for example by heat or radiation, and subsequent cooling. Due to the low average molecular masses and densities of the olefin block copolymers (OBC) and the polyolefin elastomers, but also due to their increased polarity compared to the matrix material, they move relatively freely within the polymer matrix when heated. During cooling, a thermodynamically controlled phase separation takes place, with the olefin block copolymers (OBC) and/or the polyolefin elastomers preferentially accumulating on the colder mold parts and/or on the surface or surfaces of the injection molded body.

3 shows schematically the utilization of the hotmelt adhesive functionality of the olefin block copolymers (OBC) and/or thermoplastic polyolefin elastomers (POE) now enriched on the molded body surface by reheating and subsequent gluing of the heated surface-modified injection molded body with a suitable decorative part. The heating can be carried out exclusively by microwave treatment, preferably with the support of incorporated microwave-coupleable additives. A separate adhesive application is not required. The decorative part is in particular an elastic, flat covering element, for example leather or imitation leather.

Claims (10)

Surface-modified injection molding (1), produced from a thermoplastic polymer matrix (2) and a second polymeric material (3), the thermoplastic polymer matrix (2) being selected from the group consisting of acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile ( SAN), polystyrene (PS), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyamide (PA), or mixtures thereof, and the second polymeric material (3) is a functionalized thermoplastic polyolefin elastomer (POE), is an olefinic block copolymer (OBC) or a mixture thereof, which is present at least in regions as a surface layer and is suitable as a hot-melt adhesive for connecting the injection-molded body (1) to another component, the polymer matrix (2) and the second polymeric material (3 ) have different weight-average molecular weights and polarities, the second polymeric material (3) being contained in a proportion of 10-30% by mass, u nd wherein the second polymeric material (3) has an average molecular weight of 11,000 to 37,000 g/mol. Surface-modified injection molding (1) after claim 1 , wherein the thermoplastic polymer matrix (2) and the second polymeric material (3) at least partially form a phase separation under the action of heat with enrichment of the second polymeric material (3) on the surface of the injection molded body (1) and increasing the surface tension. Surface-modified injection molding (1) according to one of Claims 1 or 2 , wherein the polymer matrix (2) and the second polymeric material (3) have different weight-average molecular weights and polarities. Surface-modified injection molding (1) according to one of Claims 1 - 3 , wherein the second polymeric material (3) can be melted and resolidified. Surface-modified injection molding (1) according to one of Claims 1 - 4 , wherein the second polymeric material is contained in a proportion of 10-25% by mass. Surface-modified injection molding (1) according to one of Claims 1 - 5 , wherein the thermoplastic polymer matrix (2) and/or the second polymeric material (3) has additives that can be coupled by microwaves. Surface-modified injection molding (1) after claim 6 , wherein the microwave-coupleable additives contain carbon fibers, carbon nanotubes, graphene. Process for producing a surface-modified shaped body (4) with the following steps: a) providing a mixture containing at least one thermoplastic polymer matrix (2) with a second polymeric material (3), the thermoplastic polymer matrix (2) being selected from the group consisting of acrylonitrile -butadiene styrene (ABS), styrene acrylonitrile (SAN), polystyrene (PS), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyamide (PA), or mixtures thereof, and the second polymeric material ( 3) a functionalized thermoplastic polyolefin elastomer (POE), an olefinic block copolymer (OBC) or a mixture thereof, which is suitable as a hot melt adhesive, wherein the polymer matrix (2) and the second polymeric material (3) have different weight average molecular weights and Having polarities, wherein the second polymeric material (3) is contained in a proportion of 10-30% by mass, and wherein the second polymeric material (3) with has an average molecular weight of from 11,000 to 37,000 g/mol; b) injection molding of the mixture in an injection mold, the thermoplastic polymer matrix (2) and the second polymeric material (3) being present in a statistically distributed manner; c) removing the molding from the injection mold; d) heating of the injection-moulded body (1), the thermoplastic polymer matrix (2) and the second polymeric material (3) at least partially undergoing a phase separation with enrichment of the second polymer Form material (3) on the surface of the injection molded body (1); and e) gluing the injection molded body (1) to a further component, the second polymeric material acting as an adhesive for connecting the injection molded body (1) to the further component. procedure after claim 8 wherein the injection molded body (1) is heated at least in regions in a gradient-controlled manner such that the second polymeric material (3) is selectively enriched on a predeterminable surface or surface area of the injection molded body (1). procedure after claim 8 or 9 , wherein the injection molded body (1) is heated at least in regions in a gradient-controlled manner in such a way that the second polymeric material (3) is selectively enriched on a visible surface of the injection molded body (1) and this is then bonded to a flat decorative part (4).

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